Throttle valve arrangement

ABSTRACT

A throttle valve arrangement includes a fixed orifice in series with a variable orifice constituted by a throttle valve member coacting with ports. The throttle valve member is spring loaded to a fully open position and has an area at one end subjected to the pressure downstream of the fixed orifice to urge the throttle valve member in the same direction as the spring loading. A smaller area at the opposite end is subjected to the pressure upstream of the fixed restrictor. A step in the valve member is subjected to pressure downstream of the variable restrictor.

May 6, 1975 l37/50l X l37/50l X Chenault.........................

ABSTRACT 2,583,296 l/l952 Harrington..................... 2,865,397 12/1958 Primary ExaminerAlan Cohan Assistant Examiner-Gerald A. Michalsky Attorney, Agent, or Firm-Holman & Stern A throttle valve arrangement includes a fixed orifice in series with a variable orifice constituted by a throttle valve member coacting with ports. The throttle valve member is spring loaded to a fully open position and has an area at one end subjected to the pressure downstream of the fixed orifice to urge the throttle valve member in the same direction as the spring load ing. A smaller area at the opposite end is subjected to the pressure upstream of the fixed restrictor. A step in the valve member is subjected to pressure downstream of the variable restrictor.

2 Claims, 1 Drawing Figure 137/501; 137/503 Fl6k 31/12 137/501, 503

THROTTLE VALVE ARRANGEMENT Inventor: Trevor Stanley Smith, Birmingham,

England Assignee: Lucas Aerospace Limited,

Birmingham, England Filed: Oct. 3, 1973 Appl. No.: 403,006

Foreign Application Priority Data Oct. 3, 1972 United Kingdom...............

References Cited UNITED STATES PATENTS l/l9l3 7/1913 Shafi'ner.....

United States Patent Smith [52] US. [51] Int. [58} Field of o 1 \s m H w 3 3 ii. is "O m 2 hi 3 Nu 8 \G v/ t ///f B 2 9 E 6 R r z F THROTTLE VALVE ARRANGEMENT This invention relates to a throttle valve arrangement for use in a gas turbine engine fuel system.

A throttle valve arrangement in accordance with the invention comprises a fixed orifice and a variable orifice in series, the variable orifice being in the form of a throttle valve member movable in a valve-closing direction against spring loading by fluid pressure, said valve member having a first portion subjected to the pressure upstream of the fixed orifice to urge the valve member towards its closed position, a second portion larger than said first portion subjected to the pressure downstream of the fixed orifice to urge the valve member towards its open position and a third portion subjected to the pressure downstream of the valve arrangement to urge the valve member towards its closed position.

An example of the invention is shown diagrammatically in the accompanying drawing.

The throttle valve arrangement shown includes a body in which a sleeve ll is fitted. The sleeve ll has an array of ports 12 which form, in combination with a throttle valve member 13, a variable orifice. The valve member 13 has gear teeth which are engaged, in use, by another gear to rotate the member l3 relative to the sleeve 11.

The member 13 is itself in the general form of a sleeve, having a cylindrical outer surface and a stepped cylindrical interior surface. The end of the member 13 having the larger internal diameter is rotatably received by a bearing 15 and is disposed in an inlet chamber 16. A spigot member I7 is mounted on the body 10 and extends into this end of the member 13 and has at its free end a head l9 of stepped cylindrical form engaging the interior surface of the member 13 on opposite sides of the step 18 thereon. The spigot member 17 is tubular and is formed with a hole 20 in its wall and a series of further holes 21 which, in combination form a fixed flow restrictor through which fluid passing from the inlet chamber 16 to the ports 12 must pass.

The body 10 has an internal groove 22 surrounding the ports 12 and this groove is connected by drillings 23, 24 in the sleeve 11 and bearing 25 therein to an external groove 26 in the member 13. Drillings in the member l3 connect the groove 26 to an annular chamber 9 defined between the head 19 and the interior of the member 13.

The throttle valve arrangement is used in combination with a gear pump 27 which is driven by the engine 28 and a centrifugal type boost pump 29 ganged with the gear pump. The outlet of the pump 27 is connected to the chamber 16 and the outlet of the pump 29 is connected both to the inlet of the pump 27 and to a chamber 30 surrounding the gear 14. The groove 22 is connected via a fuel metering system 3], which receives various input signals from the engine 28 and a manual control 32, to the burners of the engine 28. The end of the sleeve ll communicates with a spill valve 33 which is subjected to a pressure signal from the downstream side of the metering system so that the amount of fuel spilled depends on the total pressure drop through the throttle valve (ll, 12, 13) and the metering system 31.

Spilled fuel is returned to the chamber 30. A pressure relief valve 34 is connected between the end of the sleeve ll and the chamber 30 but this only opens when the valve 33 is unable to spill sufficient fuel to reduce the pressure at the end of sleeve 11 below the pressure at which valve 34 opens, e.g., when a shut-off cock 37, downstream of the system 31 and the connection therefrom to the valve 33, is shut.

In addition an electrically actuated restrictor 35, controlled by one or more signals derived from the engine, is connected between the chamber 16 and the end of the sleeve 11.

The member 13 is urged by a spring 36 to a wideopen position as shown. When fuel flows through the throttle valve arrangement, a pressure drop is created by the fixed orifice 20, 21. This pressure drop is sensed by the member 13, and a valve-closing force is applied thereto. When the valve is wide open the pressure in the chamber 9 is substantially equal to the pressure downstream of the fixed orifice. When the valveclosing force is sufficient to overcome the spring loading the valve commences to close. thereby reducing the pressure acting in the chamber 9. Thus the provision of the chamber 9 has the result of effectively increasing the rate of spring 36 and also has the effect of stabilising the valve against low frequency pressure fluctuations. The valve 33 ensures that the total pressure drop through the valve ll, 13 and the metering system is substantially constant so that the rate of fuel flow to the engine is properly controlled in accordance with both the engine parameters controlling the metering system 31 and the engine speed which is the sole factor determining the rate offuel flow through the fixed orifice 20, 2i, when the valve 35 is closed. In fact the valve 35 provides a trim for the system by by-passing some of the fuel pumped by the gear pump 27 so that the fixed orifice serves a reduced flow.

I claim:

I. A throttle valve arrangement for use in a gas turbine engine, comprising an inlet, an outlet, a fixed orifice and a variable orifice in series between said inlet and outlet, said variable orifice being on a side of said fixed orifice remote from said inlet and said variable orifice having a piston control member, a spring biasing said control member in a direction to open said variable orifice, said control member comprising a sleeve having first, second and third areas respectively responsive to the pressures on the inlet side of said fixed orifice, on the side of said fixed orifice remote from said inlet side and on the outlet side of said variable orifice, an increase in the pressure on said first and third areas urging the control member towards its closed position and an increase in the pressure on said second area urging the control member towards its open position, said sleeve having a stepped cylindrical internal surface, a tubular member extending into the interior of the control member and having a head of stepped cylindrical form engaging the interior of the control member on opposite sides of the step therein.

2. A throttle valve arrangement as claimed in claim 1 in which said tubular member incorporates said fixed 

1. A throttle valve arrangement for use in a gas turbine engine, comprising an inlet, an outlet, a fixed orifice and a variable orifice in series between said inlet and outlet, said variable orifice being on a side of said fixed orifice remote from said inlet and said variable orifice having a piston control member, a spring biasing said control member in a direction to open said variable orifice, said control member comprising a sleeve having first, second and third areas respectively responsive to the pressures on the inlet side of said fixed orifice, on the side of said fixed orifice remote from said inlet side and on the outlet side of said variable orifice, an increase in the pressure on said first and third areas urging the control member towards its closed position and an increase in the pressure on said second area urging the control member towards its open position, said sleeve having a stepped cylindrical internal surface, a tubular member extending into the interior of the control member and having a head of stepped cylindrical form engaging the interior of the control member on opposite sides of the step therein.
 2. A throttle valve arrangement as claimed in claim 1 in which said tubular member incorporates said fixed orifice. 